The sequencing of the Atlantic cod genome in 2011 demonstrated that this species lacks a crucial part of its immune system. In a follow-up study, Kjetill S. Jakobsen and collaborators have investigated a large number of additional ...

Papa might not have been a rolling stone, according to a new study that examined the mating dynamics of transient wildlife that have dispersed from other areas. The researchers found if males traveling from long distances ...

A team of international scientists has tracked the love lives of koalas, uncovering some curious behaviours and finding that male koalas make their distinct bellows to avoid confrontation with competitors.

Purdue University research found that wild-type zebrafish consistently beat out genetically modified Glofish in competition for female mates, an advantage that led to the disappearance of the transgene from the fish population ...

Female mice are attracted more strongly to the odour of healthy males than unhealthy males. This had already been shown in an earlier study by researchers from the Konrad Lorenz Institute of Ethology at the Vetmeduni Vienna. ...

Mate choice is often the most important decision in the lives of humans and animals. Scientists at the Konrad Lorenz Institute of Ethology at the Vetmeduni Vienna have found the first evidence that birds may choose their ...

A fundamental question in neurobiology is how animals, including humans, make decisions. A new study publishing in the open access journal PLOS Biology on October 7 reveals how fruit fly females make a very important decision: ...

Sexual selection

Sexual selection is the theory proposed by Charles Darwin that states that certain evolutionary traits can be explained by intraspecific competition. Darwin defined sexual selection as the effects of the "struggle between the individuals of one sex, generally the males, for the possession of the other sex". Biologists today distinguish between "male to male combat" (it is usually males who fight each other), "mate choice" (usually female choice of male mates) and sexual conflict. Traits selected by male combat are called secondary sexual characteristics (including horns, antlers, etc.) and sometimes referred to as "weapons"; and traits selected by mate choice are called "ornaments". Much attention has been given to cryptic female choice, a phenomenon in internally fertilising animals such as mammals and birds, where a female will get rid of a male's sperm without his knowledge. The equivalent in male-to-male combat is sperm competition.

Direct competition between members of one sex (usually males) for mates is also classified as intrasexual selection, while mate choice is known as intersexual selection.

Females often prefer to mate with males with external ornaments—exaggerated features of morphology. These can plausibly arise because an arbitrary female preference for some aspect of male morphology initially increased by genetic drift, creating, in due course, selection for males with the appropriate ornament. This is known as the sexy son hypothesis. Alternatively, genes that enable males to develop impressive ornaments or fighting ability may simply show off greater disease resistance or a more efficient metabolism—features that also benefit females. This idea is known as the good genes hypothesis.